If you’ve ever stood in a manufacturing facility watching a vacuum chamber cycle through its pressure steps, or waited for a vacuum-sealed bag of coffee to perk up after a long trip, you’ve probably interacted with a silicone sealing strip without realizing it. I’ve been supplying custom silicone sealing strips to industrial and lab teams for 12 years, and one question comes up more often than any other: “Can silicone sealing strips even handle vacuum applications?” Silicone Sealing Strip
The short answer is yes—but not all silicone strips are built for that use case. Over the years, I’ve seen teams reach for whatever silicone strip they have on hand, only to end up with leaks, degraded seals, or ruined parts inside their vacuum chambers. That’s why I want to break down the science, the caveats, and how to pick the right strip (or work with someone who knows how to spec it) if you’re using silicone for vacuum sealing.
First, let’s start with the basics of how vacuum sealing works. Vacuum applications rely on a hermetic, airtight seal between two mating surfaces to create a low-pressure environment—whether that’s a lab vacuum oven for curing composites, a pharmaceutical packaging line that removes oxygen to extend shelf life, or a semiconductor deposition chamber where even a single stray air molecule can ruin a wafer. For the seal to hold, the material can’t have tiny gaps, can’t outgas gases that would contaminate the vacuum, and can maintain its elasticity through repeated pressure cycles (going from atmospheric pressure to <1e-3 torr, for example).
Silicone is often a top pick here because it’s flexible, resistant to temperature extremes (from -40°F to 500°F, depending on the grade), and won’t corrode like rubber or metal alternatives. But not all silicone is equal. I remember a small biotech lab that ordered cheap general-purpose silicone strips for their vacuum freeze dryers, only to find out the strips were made with filler oils that outgassed. The freeze dryer was rendering their vaccine samples unusable for two weeks straight before they figured out the leak source—and the cheap silicone was to blame.
That brings us to the first key point: outgassing. This is the make-or-break factor for vacuum applications. Outgassing is when a material releases gases or volatile compounds into the low-pressure space. For vacuum systems, even trace amounts of outgassed products can be catastrophic. In semiconductor manufacturing, outgassed molecules can condense on wafers, ruining millions of dollars in parts. In medical vacuum systems, those same compounds can contaminate sterile equipment.
Standard general-purpose silicone strips (the kind you might use for a bathroom window seal) are filled with plasticizers, oils, or low-grade fillers to cut costs. These compounds are not designed for vacuum use. When placed in a low-pressure environment, they vaporize and escape from the silicone, creating tiny bubbles in the seal or contaminating the vacuum. That’s why when I supply silicone strips for vacuum applications, we use what’s called “high-vacuum grade” silicone—formulated with almost no volatile additives, so outgassing is well below the strict limits set by organizations like NASA or the American Society for Testing and Materials (ASTM E595).
I can’t tell you how many times a customer has said, “We used silicone before and it leaked.” Nine times out of ten, the problem was not the silicone itself, but the wrong grade. Last year, a aerospace component manufacturer reached out to me in a panic. They had been using a neoprene strip, which was too rigid and cracked in their -60°F vacuum chambers, leading to pressure loss during test flights. We swapped in a custom high-vacuum silicone strip, designed to compress just enough to form a tight seal against their aluminum chamber edges, and they haven’t had a leak in 18 months.
Next, let’s talk about compression set. Compression set is the tendency of a material to stay deformed after being squeezed, instead of bouncing back to its original shape. For a sealing strip, this is non-negotiable. If a silicone strip compresses and doesn’t spring back, it won’t form a consistent seal on the next cycle—gaps develop, air seeps in, and your vacuum pressure drops.
In vacuum applications, strips have to compress consistently, often thousands of times, without losing elasticity. General-purpose silicone has a compression set of around 20% after 22 hours at 158°F. That’s fine for a bathroom seal, but not for a vacuum oven that runs 24/7. High-vacuum grade silicone I supply has a compression set of less than 10% under the same conditions, meaning it bounces back perfectly after each use. I’ve seen cheap silicone strips that would compress permanently after just a few vacuum cycles, leading to leaks that were impossible to fix until the strips were replaced.
Another thing to consider is temperature resistance. Vacuum systems often operate at extreme temperatures. Some vacuum ovens cure parts at 400°F, while others for space simulation test drop down to -100°F. Silicone is one of the few materials that works across this range, but again, grade matters. Low-quality silicone will get hard and brittle at cold temperatures, crack, and break the seal. At high temperatures, it will soften too much, deform, and also leak. Our high-vacuum silicone is formulated to maintain its elasticity from -80°F to 525°F, so it works across nearly all standard vacuum application temperatures.
Then there’s the type of vacuum you’re working with. Not all vacuums are created equal. A rough vacuum, used in packaging or simple freeze dryers, is around 1 to 10 torr. A medium vacuum, used in many industrial processes, is 1e-3 to 1 torr. A high vacuum, used in semiconductors or space simulation, is below 1e-3 torr. The lower the pressure, the stricter the requirements for your sealing strip. For high vacuum, you need a strip that’s not just low-outgassing, but also has a smooth, uniform surface—no tiny imperfections or pores where air can seep through. That’s why we machine our high-vacuum silicone strips to a precision of +/- 0.005 inches, instead of extruding them (which can leave tiny gaps in the material).
I get asked all the time: “What about metal gaskets? Why not just use those instead of silicone?” Metal gaskets are great for very high-temperature, ultra-high-vacuum applications, but they’re rigid, hard to align, and can scratch delicate chamber surfaces. Silicone is flexible, so it conforms to slightly uneven mating surfaces—something metal can’t do. That makes it perfect for applications where a tight fit is hard to achieve, like custom-shaped vacuum chambers or portable vacuum systems.
That said, silicone isn’t right for every vacuum job. If you’re working with a corrosive gas that will break down silicone, a Viton or EPDM strip might be better. Or if you need an ultra-high-vacuum system below 1e-7 torr, some teams opt for metal gaskets. But for the vast majority of vacuum applications—from lab ovens to food packaging to medium-vacuum industrial processes—silicone sealing strips are more than capable, as long as you pick the right grade.
Over the years, I’ve built relationships with hundreds of customers who used to struggle with vacuum seals because they picked the wrong silicone strip. One of my first regular clients was a university physics lab that had gone through three different strip suppliers in six months, each time having leaks during their vacuum leak tests. They switched to our high-vacuum silicone strips four years ago, and they haven’t had a single seal failure since. That’s the kind of result that keeps me going—not just supplying strips, but helping customers understand which ones work for their specific use case.
If you’re working on a vacuum application and you’re not sure if your current sealing strip is up to par, don’t guess. Test it. If you’re noticing pressure drops, outgassing odors, or leaks, the first step is to check the grade of silicone you’re using. If you’re in the market for a silicone sealing strip designed for vacuum use, we can work with you to spec the right material, thickness, and shape for your exact chamber or equipment. Whether you need a custom-sized strip for a small lab vacuum oven or a long roll for a high-speed packaging line, we can deliver a strip that meets your vacuum requirements.
Don’t let a bad seal ruin your project. Silicone can absolutely be used in vacuum applications—you just need the right silicone. If you’re ready to talk about your vacuum sealing needs and find a solution that works for you, reach out to our team to discuss your requirements. We’ll help you pick the best silicone sealing strip for your vacuum application, no guesswork, no wasted time, no ruined parts.
Silicone Extrusion References
ASTM E595-20, Standard Test Method for Total Mass Loss and Collected Volatile Condensable Materials from Outgassing in Space Environment
NASA SP-8007, Material Selection for Spacecraft Components
ISO 10297:2016, Vacuum Technology — Sealing Materials — Silicone Rubbers for Vacuum Applications
Dongguan Hengyue New Material Technology Co., Ltd.
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